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Universal Milling Machine.                   179

The Universal Milling Machine vtas of American design in the
first place, andotie of these useful machines is shewn in Plate XII.,
as made by Messrs. Tangye.

The mandrel A is driven from the cone pulley B, either directly
or through the back gear, the latter being thrown out by the
handle c, which turns eccentric bushes as usual. The mandrel
is of large diameter, for stiffness, and revolves in coned bearings
D D, the thrust when using a face cutter being taken by the steel
tail pin E. A strong overhanging bracket F carries a small head
H and centre G, to support an edge cutter, which centre is
roughly adjusted by unbolting H, and finely by unscrewing the
check nuts. The bracket is usually made round, and that form
has some advantages, but is not so steady. The mill is either
supported between centres, and driven from the catch plate; or
has a shank similar to that described for the drill sockets at
Fig, 169, when it is further steadied by the outer centre G; the
latter is the more common method. A twin mill is shewn in
position. Sometimes tools are fixed in the holes shewn in the
catch plate at j, which is thus transformed into a face cutter, but
the points must all be placed in the same vertical plane, so that
each may take its proper share of work.

A vertical slide K, having square edges for rigidity under
heavy cuts, supports a knee bracket L, which carries the table M,
and between L and M are two slides N and p, the first for longitu-
dinal, and the'second for cross traversing. These swivel on the
circular table Q, formed by their common surfaces, and P is made
of extra kngth in plan to steady the table, a detail often
neglected. A special point is the improved means of traversing
the table. This is often effected by telescopic shafts with universal
joints connected to the end of the table, and these sometimes act
at such bad angles that the joints in crossing centres cause a slight
dwell, which is reproduced on the work. This is avoided in the
machine illustrated. A small cone pulley R on the mandrel
dri-ves the lower pulley s, keyed to the worm shaft T, This shaft
carries a worm, gearing into a worm wheel g. A telescopic shaft
u is connected to the inside of the worm wheel by a universal
joint, and to the mitre wheels vw by a corresponding joint; these
convey the motion to the screw x, whidh gives a cross feed to the